Pediatric otohns overview

Question 1

What primary germ layers make up the branchial

arches, grooves (clefts), and pouches?

Answer 1

Branchial arches and grooves (clefts) are covered externally by ectoderm and composed internally by mesoderm. Each arch has a cartilaginous, muscular, neural, and arterial component. Branchial pouches are composed of endoderm.

Question 2

What are the three most common branchial

anomalies in order of frequency?

Answer 2

● 70 to 95%: Second branchial arch anomalies
● 8 to 10%: First branchial arch anomalies
● 3 to 10%: Third and fourth branchial arch anomalies

Question 3

What branchial cleft anomaly involves the facial

nerve?

Answer 3

First branchial cleft anomaly tracts are close to the parotid
gland, particularly the superficial lobe. The tract may pass
above, between, or below the branches of the facial nerve.

Question 4

What is the second branchial arch structure that
normally regresses during development but may
be associated with hearing loss and pulsatile
tinnitus when present in the adolescent or adult?

Answer 4

The stapedial artery

Question 5

Where is the proximal opening of a second

branchial cleft anomaly?

Answer 5

Tonsillar fossa

Question 6

What artery can persist in adulthood from the

second branchial arch?

Answer 6

The stapedial artery

Question 7

What is the course of a persistent stapedial artery?

Answer 7

The stapedial artery rises from the internal carotid artery
(ICA), enters the hypotympanum via the Jacobson canal,
passes through the crura of the stapes (obturator foramen
of the stapes), then passes through the cochleariform
process and runs with the tympanic section of the facial
nerve before exiting into the extradural intracranial space
just before reaching the geniculate ganglion. It replaces the
middle meningeal artery, resulting in a hypoplastic or
aplastic foramen spinosum.

Question 8

What symptoms are associated with a persistent

stapedial artery?

Answer 8

Pulsatile tinnitus, asymptomatic incidental finding, con-
ductive hearing loss (associated stapes ankylosis), sensor-
ineural hearing loss (SNHL), erosion of the otic capsule

(rare), and may be associated with additional vascular
anomalies (i.e., the ICA)

Question 9

Describe the pathway of a third branchial arch

anomaly.

Answer 9

Piriform sinus of the hypopharynx → through the inferior
constrictor muscle medially → greater cornu of the hyoid
bone, lateral to the superior laryngeal nerve (nerve of the
fourth arch) → over the hypoglossal nerve → inferior to the glossopharyngeal nerve → posterior to the ICA → fistula
opens to the skin over the anterior border of the
sternocleidomastoid muscle (SCM)

Question 10

Describe the pathway of a fourth branchial arch

anomaly.

Answer 10

Piriform sinus of the hypopharynx → medial to the
superior laryngeal nerve (nerve of the fourth arch) →
tracheoesophageal groove, parallel to the recurrent
laryngeal nerve into the mediastinum → under the aortic
arch (left) or subclavian artery (right) (both are fourth arch
derivatives) → ascends along posterior surface of the
common carotid artery → anterior border of the SCM; it can
also follow the common carotid artery to bifurcation →
between the ICA and the external carotid artery (ECA) →
below the glossopharyngeal → above the hypoglossal →
descends inferiorly to exit anterior to the SCM

Question 11

What are the clinical presentations for third and

fourth branchial cleft anomalies?

Answer 11

Both may be noted as a soft fluctuant mass, abscess, or
draining tract located along the anterior border of the SCM.
Acute suppurative thyroiditis can be seen. Stridor may be
present in newborns with a lateral neck mass.

Question 12

What are the typical findings in a patient with

branchio-otorenal (BOR) syndrome?

Answer 12

Autosomal dominant syndrome:
● Malformed external ears
● Preauricular pits
● Conductive, sensorineural, or mixed hearing loss
● Renal anomalies ranging from mild hypoplasia to
complete agenesis

Question 13

At which cervical vertebral level is the cricoid
cartilage of an infant located? Does this location
change as the child grows?

Answer 13

The fourth cervical vertebra
The cricoid descends to the level of the seventh cervical
vertebra by adulthood.

Question 14

Why is the thyroid notch not a palpable landmark

for tracheotomy in infants?

Answer 14

Infants have a shortened thyrohyoid membrane, so the
hyoid bone is located anterior to the thyroid notch,
obscuring the thyroid notch as a landmark for tracheotomy.

Question 15

What is the diameter of the subglottis in a

full-term infant?

Answer 15

5 to 7 mm (< 4 mm indicates a subglottic stenosis)

Question 16

What are the dimensions of the trachea in a

full-term infant?

Answer 16

4 cm long × 6 mm wide.

Question 17

What is the ratio of cartilaginous to membranous

trachea?

Answer 17

4.5:1

Question 18

What additional anomaly should be actively looked

for in a patient who has a complete vascular ring?

Answer 18

Vascular sling

Question 19

Describe how infants maintain a nasopharyngeal

airway while suckling.

Answer 19

The more superior cervical position of the larynx allows
overlap of the epiglottis and the soft palate, which allows
the flow of milk or formula to be channeled around the
dorsum of the tongue and laterally around the epiglottis,
thus protecting the airway.

Question 20

What is the first paranasal sinus to develop

embryologically?

Answer 20

The maxillary sinuses begin developing at 3 weeks of fetal
life and are partially pneumatized at birth. They reach full
adult size by age 16 years.

Question 21

What is the last sinus to undergo pneumatization?

Answer 21

Frontal sinuses

Earliest pneumatization occurs at or shortly after age 2 years.

Question 22

When do the inner ear structures reach full

adult size?

Answer 22

The inner ear structures begin developing at 4 weeks’

gestation and reach adult size by 6 months’ gestation.

Question 23

At what age would you expect to see inner ear

malformations develop in a fetus?

Answer 23

Between 4 and 13 weeks’ gestation (first trimester)

Question 24

When does the auricle achieve the adult form?

Answer 24

~ 18 weeks gestation. However, it continues to grow in
childhood with changes continuing into late adult life. Adult
width and length are achieved at different times. Width:
age 6 years in females, age 7 in males. Length: 12 in
females, 13 in males); 90% of adult size achieved by age 5

Question 25

Orbital size is what percentage of the adult

size at birth?

Answer 25

60 to 65%. This is also the case for the length and width of
the cranium. The optic nerve and eye are extensions of the
brain and follow brain growth (reaches adult size by 2 or 3
years) rather than growth of the facial skeleton.